Slice the courgettes, then sauté them in a pan with 2 tablespoons of oil, half a garlic clove, salt. Keep them aside. In the same pan sauté the plum tomatoes cut in halves with 2 tablespoons of oil, the remaining garlic and salt. Beat the eggs with a little salt and a pinch of pepper, add both vegetables, a handful of basil leaves and the chopped mackerel fillets. Heat the oven to 200 degrees. Brush with oil 12 non-stick muffin moulds and put them in the well heated oven to make them warm up. Then fill them up quickly with the preparation, put them back in the oven and cook for 10-12 minutes until the frittatine are swollen and golden. Immediately unmold them by turning the mould over a tray. Serve cold or hot.